A percussion boring machine of this kind is disclosed in German Offenlegungsschrift 38 33 882, hereby incorporated by reference. There the elastic separator acts as a damping block and when the apparatus is used absorbs unavoidable shocks and vibrations in order to keep these away from the reversing mechanism as much as possible. To facilitate the assembly of the control pipe and the damping block the known percussion boring machine has radial projections on the control pipe and/or on the housing, between which the separator is retained on the control pipe and/or in the housing. Because of the elastic separator between the housing and the control pipe the oscillations and shocks caused by the rapid strokes of the piston are only transmitted to the control pipe and the compressed air hose connection after damping. Thereby fatigue fractures, particularly in the rear part of the housing, can be avoided even after use for long periods and under difficult conditions. Also the control pipe with the hose connection is no longer subjected to the heavy blows and oscillations of the housing, so that there is no risk of it unintentionally working loose. Therefore the compressed air hose can advantageously be fixed by means of a screw coupling. The overall result of this is a longer life for the percussion boring machine.
However, it has been found in use that, mostly as a result of unskillful assembly, the separator can show signs of wear and/or damage after a lengthy period of use, which is attributable to the seating of the elastic separator on the control pipe and/or in the housing being too loose.